kidd,
I know that in a previous reply that I mentioned the fact that your slab appeared to be well within the time span for treasure signs. Now I'm going to expand on that information, mainly because of the tree carvings you have posted.
I have been to sites where there were treasure signs carved into trees, however, these signs could not have been more that 10 to 15 years old. It became obvious that the "family," or, family members had come back to check on the sites to make sure that everything was fine and to update information as the older trees and cactus died off.....as Hillbilly Bob Brewer tells us these people are a form of sentinel. These treasures are of great importance, and to think that these people have forgotten about them is ridiculous. With that being said, lets move on.
Your tree carvings prove that you have a John site. The "73" carving is telling you that you need to find the triangle. Now, I know I said to stay away from the triangle but seeing this "73" adds a whole new dimension to this site.
Your first point in this triangle will be an owl shaped rock, or, at the very least, a partially buried rock that will have the number "13" on it. There will be other directions on this rock that will try to take to take you off into the triangle, but don't go there.
My suggestion is this, locate this triangle then get back to me. The rest of this information will be given to you through personal e-mails.